Question

Working in C, modify the algorithm created in the Topic 1 assignment "Non-Linear Flow Chart" to instead compute the nth term in the series by calling a recursive function. Note that the value of "n" will need to be an input argument, along with the two starting values of the series. Discuss the efficiency of this method versus the iterative logic that you wrote previously.

Previous Code:

//main.c

#include<stdio.h>

#include<limits.h>

int main()

{

   //declare a integer data type variales

   int first;

   int second;

   int result=0;

   //Set INT_MAX as max value

   int max=INT_MAX;

   printf("Enter first value :");

   scanf("%d",&first);

   printf("Enter second value :");

   scanf("%d",&second);

   printf("%d,",first);

   printf("%d,",second);

   //Add the two values and store sum in result variable

   result=first+second;

   /*Loop till result is less than max value*/

   while(result<=20000)

   {

       //print result value

       printf("%d,",result);

       //Assign second value to first

       first=second;

       //Assign the result to second

       second=result;

       //Add two values and assign sum to result

       result=first+second;

       //Break the loop if result is less than 0

       if(result<0)

           break;

   }

   return 0;

}

Answer 1

#include<stdio.h>

#include<limits.h>
//recursive function
//which returns the nth term in the series
int nthTerm(int s1,int s2,int n)//input:n value and two starting values
{
   if(n==1)
   return s1;
   if(s1+s2 == 0)
   return -1;//means proper posivite value are not given //so stopping here
   return nthTerm(s2,s1+s2,n-1);//recursive call
}
//complexity of both iterative and recursive methods is same : O(n)
int main()

{

//declare a integer data type variales

int first;

int second;

int result=0,n;

//Set INT_MAX as max value

int max=INT_MAX;

printf("Enter first value :");

scanf("%d",&first);

printf("Enter second value :");

scanf("%d",&second);

printf("Enter n value to find nth term in the series:");
scanf("%d",&n);
result = nthTerm(first,second,n);
printf("%dth term in the series is :%d\n",n,result);
return 0;

}

output:

Enter first value :1
Enter second value :2
Enter n value to find nth term in the series:5

5th term in the series is :8